1. Field of the Invention
The present invention relates to a decoding device suitable for a context-based adaptive binary arithmetic coding (CABAC) technique allowing a real-time decoding of high-definition video.
2. Description of the Related Art
H.264/AVC (Advanced Video Coding) is a video compression standard developed by the ITU-T VCEG (Video Coding Experts Group) together with the ISO/IEC MPEG (Moving Picture Experts Group) and advantageously provides more effective video compression and enough flexibility for a wide variety of network environments.
H.264/AVC realizes higher compression efficiency through advanced entropy encoding schemes including context-based adaptive variable length coding (CAVLC) that selects a table according to circumstances of neighbor blocks and thereby performs a coding, and context-based adaptive binary arithmetic coding (CABAC) that estimates probability adapted to circumstances of neighbor blocks and thereby performs an arithmetic coding.
Among them, CABAC has better compression efficiency than CAVLC and, contrary to CAVLC, encodes other syntax elements in a slice as well as DCT coefficient.
FIG. 1 shows a basic structure of a normal CABAC encoding device. Referring to FIG. 1, the CABAC encoding device performs a binarization of syntax elements through a binarization unit 110 and then, through a binary arithmetic coding unit 130, performs a binary arithmetic coding of binary signals outputted from the binarization unit 110. At this time, a context modeling unit 120 calculates the probability of occurrence of binary signals according to surrounding circumstances and offers it to the binary arithmetic coding unit 130. Then the binary arithmetic coding unit 130 performs a binary arithmetic coding of binary signals while referring to a probability value.
However, in case where video images are encoded through CABAC with good compression efficiency, a decoding may require too much higher processing speed. Specifically, due to characteristics of BAC, a single bin (i.e., a single bit forming a bin string corresponding to a symbol in a binarization process) should be completely decoded in order for the next bin to start to be decoded. Unfortunately, this may make it difficult to realize a parallel processing in a CABAC decoding process.